1. Field of the Invention
The present invention relates to a method for manufacturing a bonded wafer by an ion implantation delamination method, and particularly to a method for manufacturing a bonded wafer by an ion implantation delamination method using a reclaimed wafer obtained by subjecting a delaminated wafer produced when a bonded wafer is formed by the ion implantation delamination method to a reclaiming process.
2. Description of the Related Art
A method of manufacturing a SOI wafer by delaminating ions-implanted wafers after bonding, i.e., an ion implantation delamination method (a technique also referred to as the Smart Cut method (registered trademark)), has attracted attention as a method of manufacturing silicon on insulator (SOI) wafers, particularly a method of manufacturing SOI wafers having a thin SOI layer that enable improvement in performance of advanced integrated circuits.
This ion implantation delamination method is a technique to form an SOI wafer (See Patent Literature 1) in the following manner: an oxide film is formed on at least one of two silicon wafers; gas ions such as hydrogen ions or rare gas ions are implanted from a front surface of one of the silicon wafers (a bond wafer) to form the ion implantation layer (also referred to as a micro bubble layer or an enclosed layer) in the interior of the wafer; the surface from which the ions are implanted is then brought into close contact with the other silicon wafer (a base wafer) through the oxide film; a heat treatment (a delamination heat treatment) is then performed to cleave one of the wafers (the bond wafer) along the micro bubble layer so that the bond wafer is separated into a thin film; and another heat treatment (a bonding heat treatment) is then performed to strengthen a bond between the wafers. At this point, the cleavage plane (the delamination surface) is a surface of an SOI layer, and an SOI wafer having a thin SOI with high uniformity is relatively easily obtained.
The ion implantation delamination method is not limited to the case where a bonded SOI wafer is manufactured by bonding two wafers thorough an insulator film, but also applied to the case where the wafer is manufactured by bonding the wafers directly.
In this ion implantation delamination method, a wafer can be repeatedly by subjecting again a bond wafer after delamination (a delaminated wafer) to a reclaiming process (refreshing process) including surface treatment such as polishing and etching to reduce or eliminate the influence of a step formed at an unbonded portion, surface roughness after delamination, and a remaining implantation layer. As to the reclaiming process, for example, there has been proposed a method of combining chamfer processing and polishing to remove the influence of an ion implantation layer remaining at a chamfer portion, as described in Patent Literature 2.
Regarding the reclaiming process performed on the delaminated wafer, a subject matter that a polishing stock removal of the delaminated wafer surface is 2 μm or more and the delaminated wafer is repeatedly used as the bond wafer, is described in Patent Literature 3. Moreover, in Patent Literature 4, a subject matter that the delaminated wafer can be repeatedly polished about 5 μm at most 10 times for repeatable use, is described. Further, in Patent Literature 5, a subject matter that a polishing stock removal of the delaminated wafer surface is 1 to 5 μm or more and the delaminated wafer is subjected to a reclaiming process many times, is described.